Light source power based on predetermined sensed condition

ABSTRACT

A medical instrument having a lighting system for illuminating a target area, the system comprising a light source and associated power controller, the system being configured to move from a first illumination mode to a second illumination mode based on a sensed or determined changed condition, such as predetermined temperature and/or change in a scene or brightness signal, or lack of change, from an image sensor that may be associated with the instrument.

RELATED APPLICATIONS

This application claims the benefit of and priority to U.S. ProvisionalApplication Ser. No. 60/912,329, filed Apr. 17, 2007, the contents ofwhich are hereby incorporated by reference as if recited in full hereinfor all purposes.

BACKGROUND

The inventive subject matter generally relates to power control for alight source for a handheld medical instrument for intracorporeal use.The inventive subject matter particularly relates to solid statelighting sources, such as LEDs, used in an endoscope.

Although not limited to the use in an endoscope, the inventive subjectmatter will be illustrated by reference to endoscopic light systems,particularly those using electronic image sensors and LED light sourcesdisposed on or in an endoscope.

In order to eliminate the heavy, bulky and awkward fiberoptic “lightpipe” from a conventional light source (i.e., 300 W Xenon), high-power,white LEDs are currently used as an endoscope light source. The LEDs arecontained in the body of an digital endoscope. Such LEDs, while moreefficient than a conventional light source, produce some significantheat when operating at a high light output. Accordingly, there is a needto control the temperature of the body of the endoscope to a maximum ofabout 40° C. to meet with operator comfort or safety requirements, andpreferably to keep the instrument temperature even lower than that foroperator comfort and confidence.

Current designs vary the output of the LEDs as part of the electronicexposure system and strive to keep the temperature below the prescribedlimit by simply setting a maximum current limit. If the imaging systemsenses a situation with insufficient light, it increases LED output upto the maximum, if needed, and keeps it there if the scene still seemsto be insufficiently lit. A drawback to the approach of a set maximumpower to the LEDs to control the temperature is that the potential ofusing a higher LED output capability for short periods of time iscompromised.

Another problem with current LED systems is their failure tointelligently adapt to state of activity. For example, it is notuncommon for an electronic endoscope to be placed on a table or cart andleft for some period of time, with the end pointing toward objects muchfurther away than the designed operating distance of the endoscope, withlighting conditions which the endoscope will determine as insufficient.These conditions can set the LED drive to its maximum output, and thehandle will heat up to the set maximum temperature. A user coming backto pick up the endoscope will sense a rather hot object.

Accordingly, there is a need for improved illumination systems withautomated temperature control and intelligent adaptation to their stateof activity.

SUMMARY

The inventive subject matter provides an improved system for managingpower to an illumination source on board an instrument. In doing so, itaddresses, among other things, the need for temperature management in anelectronic endoscope, for example.

In certain embodiments, the inventive subject matter is directed to amedical instrument having a lighting system for illuminating a targetarea, the system comprising a light source for illuminating anintracorporeal target area and associated power controller, the systembeing configured to move from a first illumination mode to a secondillumination mode based on an input into the system of a predeterminedchanged condition such as whether or not the instrument is in activeuse. The medical instrument may be a handheld instrument and the lightsource is disposed within a housing that comprises the handle of theinstrument. The medical instrument may be an endoscope having asolid-state light source on or in the instrument for illuminating atarget area. The medical instrument may have a light source disposed ina handle portion of the instrument. The medical instrument may have alight source disposed in a distal insertion end of the instrument. Themedical instrument may have an image sensor disposed within a distalinsertion portion of the instrument. The medical instrument may beconfigured to adapt to a state of activity by sensing a predeterminedchange of scene or brightness or lack of change, and make apredetermined change in power to the light source based on the change orlack thereof in scene or brightness. The medical instrument may have aset of predetermined pixels in one or more image sensors that aredesignated for providing signals which are processed to determinewhether there is a predetermined change in scene or brightness. Themedical instrument may be configured to sense a predetermined change oftemperature and make a predetermined change in power to the light sourcebased on the change in temperature. The medical instrument may bebattery powered. The medical instrument may be adapted to maintain thetemperature of a surface of the instrument held or otherwise contactedby a user at a temperature of below about 40 degrees C. or some otherpredetermined safety or comfort temperature.

In other possible embodiments, the inventive subject matter is directedto a medical instrument, comprising an imaging system and anillumination system, the imaging system comprising a pixellated imagesensor; and the illumination system comprising one or more solid-statelighting devices, the instrument being configured so that a state ofactivity of the instrument is determined by processing signals from oneor more pixels in the image sensor, and a power mode for the instrumentis determined according to an output of the processing. In theembodiments disclosed herein, the power mode may be a power setting forthe illumination system. In the embodiments disclosed herein, the systemmay determine a state of inactivity of use based on processing of thesignals and provides reduced power to the illumination system based on apredetermined period of inactivity. In the embodiments disclosed herein,the medical instrument may use any the input for determining a conditionor state of use that comprises a signal from a piezoelectric sensor oran accelerometer associated with the instrument.

In yet another possible embodiment, the inventive subject matter isdirected to a method of making a medical instrument, comprising:disposing in a housing for a medical instrument an illumination systemcomprising one or more light sources; configuring the illuminationsystem with a power controller that determines power to the light sourceaccording to a state of activity for the instrument; and configuring theinstrument to determine state of activity according to processing ofsignals from an image sensor. In the method, the instrument may comprisean endoscope having the image sensor at a distal insertion end of ahousing for the endoscope and solid state light source in the housing,the instrument being configured to reduce power to the light sourceafter processing the signals to an output indicative of inactivity.

In addition to the medical instrument, the inventive subject matterextends to methods of using the instrument, systems thereof, and machineexecutable instructions in a storage media for implementing novel stepsof power control, according to the inventive subject matter.

These and other embodiments are described in more detail in thefollowing detailed descriptions and the figures.

The foregoing is not intended to be an exhaustive list of embodimentsand features of the present inventive concept. Persons skilled in theart are capable of appreciating other embodiments and features from thefollowing detailed description in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The following figures show embodiments according to the inventivesubject matter, unless noted as showing prior art.

FIG. 1A is a schematic, pictorial illustration of a system forendoscopy, in accordance with an embodiment of the present invention.

FIG. 1B is a schematic, pictorial illustration showing details of thesystem of FIG. 1A, in accordance with an embodiment of the presentinvention.

FIG. 2 is a block diagram that schematically shows circuitry forcontrolling image brightness, in accordance with an embodiment of thepresent invention.

FIG. 3 is a timing diagram that schematically illustrates adjustments ofgain and shutter speed in an electronic imaging system, in accordancewith an embodiment of the present invention.

FIG. 4 is a flow chart that schematically illustrates a method forpredictive control of image brightness, in accordance with an embodimentof the present invention.

FIG. 5 is a flow chart that schematically shows details of a method forpredictive control of image brightness, in accordance with an embodimentof the present invention.

FIG. 6A is an electronics block diagram shown without an LED CurrentControl.

FIG. 6B is an electronics block diagram shown with an LED CurrentControl according to the inventive subject matter.

FIG. 6C is a sample electronic block diagram according to the inventivesubject matter.

FIG. 7 is a flow chart showing one possible process for power controlaccording to the inventive subject matter.

DETAILED DESCRIPTION

Representative embodiments according to the inventive subject matter areshown in FIGS. 1-7, wherein similar features share common referencenumerals.

In one example embodiment of the inventive subject matter, a medicalinstrument such as an endoscope includes a temperature-sensing LED drivecontrol to the system which will limit the power input to the LED basedon keeping the handle temperature below the about 40° C. limit. Thiswould allow higher output power from the LEDs for short periods of timeif the handle temperature were below the maximum.

In another example embodiment of a medical instrument such as anendoscope includes an automatic power reduction mode based on (1) aself-timer; (2) detected scene changes; and/or (3) overall power outputin order to address the situation where the endoscope is left alone forsome period of time. This is a situation where the LED light sourcecould run at a maximum due to insufficient scene light under the currentdesign, but using the inventive subject matter reduces the LED outputafter a period of inactivity and thus the handle surface would be coolerat these times.

In other embodiments, a medical instrument may be configured with both atemperature sensing system and a scene change system. For example, onesystem could be a back-up or supplementation of the other.

In other embodiments a condition change other than a temperature orscene changed could be correlated with a power setting for the lightsource. For example, the handle of the instrument could include apiezoelectric sensor that could sense whether or not the instrument isbeing held, and power down the light source a predetermined degree if itis not. As another example, a solid-state accelerometer could bedeployed to determine whether or not there has been a predeterminedchange in position of the instrument and determine power to the lightsource accordingly.

In the foregoing embodiment, a typical user configuration provides forreduction in power to the light source if there is an indication ofinactivity, such as no change in scene, over a period of one to threeminutes. A two minute period of inactivity leading to power reduction isa most typical configuration.

The following discussion introduces a basic, example hardware platformover which the inventive subject may be used. From this discussion,persons skilled in the art will appreciate how to adapt the platform foruse in monitoring for changes in image data that correlate with apredetermined condition for adjusting the power level of an illuminationsource. This platform is illustrative and not intended to limit thescope of the inventive subject matter.

FIGS. 1A and 1B schematically illustrate a system 20 for endoscopicimaging of a body cavity 22, in accordance with an embodiment of theinventive subject matter. Cavity 22 represents a chamber 24, which isaccessed through a lumen 26. Chamber 24, for example, may be the urinarybladder of a patient, in which case lumen 26 is the urethra. As anotherexample, chamber 24 may be the stomach, in which case lumen 26 is theesophagus. The principles of the present invention are similarlyapplicable to other body cavities or passages, as will be apparent tothose skilled in the art.

Furthermore, although the example embodiments described herein belowrelate specifically to endoscopic imaging, the principles of the presentinvention may also be applied to electronic imaging systems of othertypes.

System 20 comprises an endoscope insertion shaft or tube 30, having animage sensing assembly 32 and an illumination source 34 at its distalend. The endoscope includes a handle portion 100. As used herein,“handle” means any portion of the endoscope or other instrument graspedor in contact with a user. The detailed structure of the endoscope, andparticularly of the assemblies at the distal end, may be as described inPCT patent publication WO 03/098913, for example, whose disclosure is inits entirety incorporated herein by reference. Image sensing assembly 32typically comprises an image sensor, such as a CMOS or CCD image sensor,with suitable objective optics. In an alternative embodiment (not shownin the figures), the image sensing assembly is located at the proximalend of the insertion tube and is coupled to receive images from thedistal end via a fiberoptic image guide or relay optics.

Illumination source 34 may be a light source, such as an LED, located atthe distal end of the endoscope insertion tube. Alternatively, theillumination source may be a fiberoptic light guide, with a connectionto a suitable light source at the proximal end of the endoscope.

Insertion tube 30 may be coupled to a camera control unit (CCU) 36,which controls the functions of the endoscope and processes imagesignals generated by image sensing assembly 32. Typically, the CCU isremote from the endoscopic instrument. The coupling may be by physicalconduits or wireless transmitters and receivers. The CCU typically isdisposed in a console 36. The CCU 38 receives and processes the signalsto produce a standard video output. CCU 38 may also output controlsignals to assembly 32 for controlling functions such as the shutterspeed and gain of the image sensor. An optional illumination controller40 in console 36 regulates the level of light that is output by distalillumination source 34. The functions of the CCU and illuminationcontroller are regulated by a control processor 42, using methodsdescribed herein below. Although the CCU, illumination controller andcontrol processor are shown and described herein as separate functionalunits, for the sake of conceptual clarity, some or all of the functionsof these elements may be integrated in a single processing circuit,comprising one or more integrated circuit chips.

Video images generated by CCU 38 are displayed on a video displaydevice, such as a video monitor 44. In the situation illustrated in FIG.1B, in which the distal end of insertion tube 30 is located within lumen26, the displayed image typically is a dark central region 46,corresponding to the bore of the lumen, and a brighter peripheral region48 showing the walls of the lumen. As the endoscope is advanced orwithdrawn through the lumen, the overall brightness of these regions ofthe image changes slowly, if at all, since the topology and nature ofthe tissue viewed by image sensing assembly 32 do not change.

On the other hand, when the insertion tube enters chamber 24, the wallof the chamber will come into view. As the distal end of the insertiontube approaches the wall, the intensity of the light (flux per unitarea) incident on the wall from illumination source 34 will increaseapproximately as the inverse square of the distance between the distalend and the wall. At the same time, the relative intensity of lightreflected back from the wall and captured by sensor assembly 32 willalso increase approximately as the inverse square of the distance. As aresult, the brightness of the image captured by the image sensor willincrease or decrease very abruptly as the distal end of the insertiontube moves toward or away from the chamber wall: roughly as the inversefourth power of the distance. Methods of automated brightness controlthat are known in the art are generally incapable of keeping pace withsuch rapid brightness changes, leading to temporary loss of imagevisibility due to saturation or cutoff of all or part of the image.Control processor 42 may use a novel control method, based on thetopology of cavity 22, in order to avoid this loss of image visibility.Details of this method are presented below with reference to FIG. 4.

FIG. 2 is a block diagram that schematically shows details of imagesensing assembly 32 and console 36, including CCU 38, in accordance withan embodiment of the present invention. As noted above, the imagesensing assembly comprises an image sensor 50, such as a CMOS imagesensor. The image sensor chip in this case may include ancillarycircuitry. For example, the ancillary circuitry may be any one or moreof the following: an on-board electronic shutter control 52; outputamplifier 54; and analog/digital converter (ADC) 56. Alternatively, someor all of these ancillary circuit elements may be located on a separatechip. Further alternatively, some of the ancillary circuitry, such asADC 56, may be contained in CCU 38.

In this embodiment, a preprocessor 60 in CCU 38 receives the digitizedsample stream that is output by image sensor 50. Typically, preprocessor60 comprises an integrated logic array, such as a field programmablegate array (FPGA), which operates on the digitized samples to computeactual digital pixel values. A digital signal processor (DSP) 64comprises a level adjuster 68, which scales the pixel values, and animage processing block 69. A video encoder 66 converts the stream ofpixel values into a standard video output signal. Preprocessor 60 iscoupled to a buffer memory 62, typically a dualport RAM buffer, in orderto match input and output pixel rates and compensate for processinglatency if necessary.

Control processor 42 also receives information regarding the outputsample stream (or the actual sample stream itself) from preprocessor 60,and processes this information in order to determine appropriatesettings of the sensor shutter speed and gain. Processor 42 thengenerates appropriate control inputs to sensor 50, either directly (asshown in this figure) or via CCU 38 (as shown in FIG. 1E). Additionallyor alternatively, processor 42 generates a gain control output to DSP64, for controlling the level of the output video signals. Typically,processor 42 comprises a general-purpose or embedded microprocessor,which is programmed in software to carry out the functions describedherein.

FIG. 3 is a timing diagram that schematically shows gain and shutterspeed settings that are determined and applied by control processor 42,in accordance with an embodiment of the inventive subject matter. Inthis embodiment, it is assumed that the level of light that is incidenton sensor 50 is gradually decreasing over time, requiring a concomitantincrease in the exposure time provided by shutter control 52. In thissimplified example, it is also assumed that illumination source 34 isalready operating at full intensity, or that the intensity of theillumination source is fixed, so that illumination controller 40 cannotbe used to adapt to the decreasing level of incident light.Alternatively, the control method exemplified by FIG. 3 may be modifiedto include control of illumination level, as will be apparent to thoseskilled in the art. Although this embodiment shows how processor 42adapts to decreasing light level, the method used in this embodiment issimilarly applicable in adaptation to increasing light level.

As noted above, image sensor 50 may be a CMOS sensor, which has aconventional rolling shutter. Rolling shutter operation is described,for example, in a Kodak application note entitled “Shutter Operationsfor CCD and CMOS Image Sensors” (Revision 2.0, Dec. 17, 2003), which isavailable at www.kodak.com/go/imagers and is incorporated herein byreference. This mode of operation introduces an inherent delay of atleast one video frame between the time at which an image is captured andcontrol processor 42 determines, based on the image, that a change inshutter speed is needed and the time at which the change is actuallycarried out by shutter control 52. In other words, if a frame n iscaptured, and after analyzing this frame, processor 42 signals shuttercontrol 52 at the beginning of frame n+1 to increment the shutterperiod, the change in shutter speed will actually occur only in framen+2.

In order to compensate for this delay, processor 42 applies a gainincrease to the output of sensor 50 during frame n, roughly concurrentlywith instructing shutter control 52 to increase the shutter duration. Inother words, as shown in FIG. 3, at time T1 processor 42 simultaneouslysignals shutter control 52 to increase the shutter duration (i.e., toincrease the charge integration time of the elements of sensor 50) andincreases the gain applied to the sensor output. One frame later, attime T2, processor 42 reduces the gain to compensate for the increasedsensor signal level due to the increased shutter duration. In systemsknown in the art, the gain may be decreased simultaneously with thecommand to increase the shutter duration. In system 20, however,processor 42 first increases the gain, and then decreases the gain oneframe later in order to account for the inherent delay of the rollingshutter in sensor 50.

The gain increase shown in FIG. 3 may be applied to output amplifier 54.Alternatively or additionally, control processor 42 may instruct DSP 64to adjust the gain applied to the current frame in the output videosignal. Processor 42 may compute the appropriate gain to apply to thecurrent frame while the frame is held in memory 62, and may theninstruct DSP 64 to apply this gain to the same, current frame usinglevel adjuster 68, while instructing sensor 32 to apply the same gainchange in amplifier 54, which will affect the next frame. Thisarrangement permits rapid gain adaptation in response to changes in thebrightness of the image generated by sensor 50. Processor 42 theninstructs shutter control 52 to increase the shutter duration andaccordingly decreases the gain applied by the DSP in the next frame.

FIG. 4 is a flow chart that schematically illustrates a method appliedby processor 42 in controlling image brightness in system 20, inaccordance with an embodiment of the present invention. The method isdescribed, for the sake of simplicity, with reference to gain control,but the method may also be applied, alternatively or additionally, incontrolling shutter speed and/or illumination intensity. The method iskeyed to the topological characteristics of body cavity 22 (FIG. 1B),but the principles embodied in the method may alternatively be adaptedfor use in topologies of other types.

The method is initiated when control processor 42 detects a change inthe image brightness level, at an intensity detection step 80. Thechange is typically due to an increase or decrease in the intensity ofthe light that is incident on image sensor 50. The change may bedetected, for example, in terms of a change in the average the pixelvalues output by the image sensor or a change in certain histogramcharacteristics. The change may be a global change, with respect to allthe pixels in the image, or may be in one particular area of the image,such as central region 46 (FIG. 1B). Although the method as describedherein relates to adjusting the gain applied to all the pixels in theimage, the principles of this method may be used, alternatively oradditionally, in adjusting regional gains that are applied to differentareas of the image.

Upon detecting the change in brightness, processor 42 checks thetopological characteristics of the region in which the distal end ofinsertion tube 30 is located, at a topology determination step 82. Inthe present example, the processor determines whether the distal end isinside lumen 26 or whether it is in chamber 24. The processor typicallymakes this determination automatically, by analyzing characteristics ofthe current image and possibly characteristics of a number of precedingimages, as well. For example, the processor may analyze morphologicaland/or local brightness characteristics of the image. As anotherexample, the processor may analyze changes in image brightness over thecurrent and preceding images. Another method, based on image brightnessand speed of the insertion tube in the body cavity, is described hereinbelow with reference to FIG. 5. As noted above, the image brightness isexpected to change only slowly within lumen 26, but may change rapidlyas the endoscope approaches or moves away from the wall of chamber 24.The rate of change of brightness is thus indicative of the localtopology. Additionally or alternatively, a user of system 20 may inputinformation to the system, indicating when the endoscope is in lumen 26and when it has entered chamber 24.

If processor 42 determines that the distal end of insertion tube isinside lumen 26 (or at some other location far from the wall of chamber24), the processor may apply a normal gain control algorithm indetermining the gain adjustment that is to be made in response to thecurrent intensity change, at a normal gain control step 84. Typically,the gain to be applied in frame n+1 is determined by the gain in thepreceding frame g_(n) and by the change in image brightness A in anadaptive relation of the form: g_(n+1)=g_(n)−αΔ^(γ), wherein α and γ arepredetermined constants. Under normal gain control, at step 84, α<<1 andγ≦1. This control algorithm avoids rapid gain excursions that may bedistracting to the eye of the user of system 20.

On the other hand, if processor 42 determines that the distal end of theinsertion tube is approaching or receding from the chamber wall, itapplies accelerated gain adjustment, at an accelerated gain control step86. The accelerated gain adjustment takes into account the strongdependence (typically fourth-power, as explained above) of thebrightness on the distance of the distal end from the chamber wall inorder to predict the expected level of the image signals and to adjustthe gain accordingly. For example, a Kalman filter or linearextrapolation may be applied to a sequence of image brightnessmeasurements collected over a certain number of frames. Alternatively oradditionally, an adaptive relation may be used, like the formula forg_(n+1) given above, in which the values of α and/or γ are increasedsubstantially relative to the normal mode. The accelerated gainadjustment permits system 20 to adapt rapidly to the changes inbrightness that occur when the insertion tube is facing the wall ofchamber 24 or is approaching or receding from some other surface incavity 22.

FIG. 5 is a flow chart that schematically illustrates a method forperforming predictive gain control in a changing physical environment,which may be used with the inventive subject matter described herein.The method is carried out following acquisition of each image frame, atan image acquisition step 90. Based on the image, control processor 42calculates a measure of the image brightness, at a brightnessmeasurement step 92. Any suitable statistical brightness measure may beused, as described above. The control processor also estimates the speedof motion of the insertion tube within the body cavity, at a speedestimation step 94. The speed may be estimated by means of imageprocessing, for example, by identifying an image feature in one frame,and then detecting the change in position and/or size of the samefeature in successive subsequent frames. Alternatively or additionally,the speed may be measured directly using a motion sensor, such as anaccelerometer (not shown in the figures), in or coupled to the insertiontube.

Based on the estimated speed and on the brightness of the precedingframe or frames, processor 42 computes the expected brightness of thecurrent frame, at a brightness prediction step 96. This computation isbased on the current physical model (i.e., the topological model) of thepart of the body cavity in which the insertion tube is located. In otherwords, if the insertion tube is located in lumen 26, it is expected thatthe brightness will change slowly from image to image, and processor 42will thus apply a physical model that assumes slow variation of thebrightness with the speed. For example, the expected brightness may becalculated as a linear function of the speed and the previous framebrightness. On the other hand, with chamber 24, image brightness isexpected to vary with the inverse fourth power of the distance of thedistal end of the insertion tube from the chamber wall. Therefore,processor 42 may apply a physical model in which the frame brightnessvaries roughly as the fourth power of the speed, weighted by thedistance from the chamber wall.

Processor 42 compares the actual brightness of the current frame fromstep 92 to the expected brightness from step 96, at a brightnesscomparison step 98. If the difference between the brightness values isless than a predetermined threshold, the processor concludes that thecurrent physical model is the correct one. Under these circumstances,the insertion tube is determined to have remained in the part of thebody cavity (lumen or chamber) in which it was located previously. Inthis case, the processor goes on to calculate the gain to be applied tothe next image frame based on the current physical model (lumen orchamber) and the current frame brightness, at a gain computation step102.

If the difference between the actual and expected brightness at step 98is greater than the threshold, however, processor 42 may determine thatthe insertion tube has moved into a region with a different topology.For example, if the actual brightness is significantly greater than theexpected brightness while the insertion tube is moving forward, theprocessor may determine that the insertion tube has entered chamber 24and is capturing images of the chamber wall. In this case, the processorchanges the physical model that will be used in the gain computation, ata model update step 100. The gain for the next frame is computedaccordingly at step 102, and the process continues from step 90.

FIG. 6A shows an electronics block diagram for an imaging system 10without control of current to an LED light system. The system includesan image sensor such as a CMOS sensor 12. The system includes a lightsource 14, such as one or more LEDs. An LED drive 15 for powering an LEDis coupled to the one or more LEDs. One or more controllers orprocessors communicate with one or more system components to processdata and instructions. In this block diagram a controller 16communicates with a user interface subsystem comprising a manual controlbutton 18 and a user control interface 20. A system clock 22communicates with a data communications interface 24 and the imagesensor.

FIG. 6B shows the system 10 configured with a current controller 26 thatcontrols the level of current provided via the LED drive 15. The currentcontroller processes input from a sensor that monitors conditions thatcorrelate with a state of the device in which system 10 is associated.For example, the sensor 26 may be a temperature sensor that monitors thetemperature of the handle of the device. The following section providesmore details about such an example system.

Temperature Sensing Drive Control

A temperature sensing drive control for a light source, such as one ormore LEDs, could be a relatively simple transistor circuit whichnormally allows full current to pass through to the LED(s) but can actas a current limiter based on input from a temperature sensor mounted inthe endoscope handle, designed to keep handle temperature below apredetermined level, for example about 40° C. In this and otherembodiments, the current limiter could be controlled either in a binaryon/off fashion or to provide variable current for a range of lightoutput.

This system could be implemented in several ways. For example, in onepossible approach the system would consist of a thermal sensor(thermistor, RTD, thermocouple, or hybrid IC) in good thermal contactwith, for example, an endoscope handle. The CCU would then condition thesignal from this sensor directly. The CCU software would then control orlimit the drive to the LED to limit the maximum handle temperature. Inthe second approach a separate circuit in the endoscope itself wouldcondition the signal from the thermal sensor. This circuit could consistof a standalone embedded controller or similar device. This device couldrun firmware or similar code to then control and monitor the LED drivecurrent and regulate handle temperature independent of the CCU. A thirdapproach would utilize the thermal sensor with the embedded controllerin conjunction with the CCU and system software.

Inactivity Monitoring Drive Control

Referring particularly to FIG. 7, in another possible embodiment,machine executable instructions stored in an appropriate media would:

-   -   a) have an inactivity timer running with a predetermined time        limit    -   b) be capable of sensing predetermined changes in the scene the        sensor is detecting (either the entire area or in one or more        areas of interest; could be limited to one or only a few        predetermined pixels where in one possible implementation the        value(s) would be monitored and compared to a range based on the        initial value(s): if a new value exceeded the (appropriate)        range then a scene change would be indicated)    -   c) reset the inactivity timer when scene changes were detected    -   d) if no scene changes were detected during the predetermined        time limit, (perhaps also when the LED drive exceeded a        threshold drive level) the LED drive level would be limited to a        predetermined power level and there would be a continued        monitoring for scene changes.    -   e) if the inactivity power reduction mode was engaged and a        scene change was detected, the limit on the LED drive level        would be removed and the inactivity timer would be reset.        The stored instructions may be implemented in any of various        known manners, such as software, firmware, or a FPGA.

Exemplary, systems and applications in which the inventive subjectmatter herein may be used include those disclosed by InternationalPublication No. WO2006/032013, published Mar. 23, 2006, entitled“Endoscopy Device Supporting Multiple Input Devices,” which is herebyincorporated by reference in its entirety. International Publication No.WO2006/032013 discloses, among other things a remote-head imaging systemwith a camera control unit capable of supporting multiple input devices.The camera control unit detects an input device to which it is connectedand changes the camera control unit's internal functionalityaccordingly. Such changes include, for example, altering clock timing,changing video output parameters, and changing image processingsoftware. In addition, a user is able to select different sets ofsoftware program instructions and hardware configuration informationbased on the head that is attached. The remote-head imaging systemutilizes field-programmable circuitry, such as field programmable gatearrays (FPGA) in order to facilitate the change in configuration. Thissystem would allow for the alteration or customization of power settingsaccording to predetermined conditions.

Exemplary systems and applications in which the inventive subject mattermay be used in include those disclosed by United States Publication No.US2005/0250983, published Nov. 10, 2005, entitled “Endoscopic InstrumentHaving Reduced Diameter Flexible Shaft,” which is hereby incorporated byreference in its entirety. United States Publication No. US2005/0250983discloses, among other things, a medical instrument comprising aflexible, filamentous shaft slideably disposed in a sheath, theinstrument including an electronic imaging system comprising an imagesensor carried on a distal end portion of the instrument. The shaft maybe used as a guidewire for a complementary guided device, or it may beused to carry a functional element for performing a procedure at atarget site in a patient's body. In other embodiments, the presentinvention contemplates a flexible sheath, preferably having a simpletubular construction, with an electronic imaging system at its distalend. The sheath is adapted to slideably receive a shaft, preferably afilamentous shaft, which closely fits the sheath. The shaft carriesfunctional element at its distal end. The instruments according to thepresent invention may include one or more filaments along their lengthfor deflecting an insertable portion of the instrument.

Exemplary systems and applications in which the inventive subject mattermay be used in include those disclosed by United States Publication No.US2006/0173242, published Aug. 3, 2006, entitled “Hermetic EndoscopeAssemblage,” which is hereby incorporated by reference in its entirety.United States Publication No. US2006/0173242 discloses, among otherthings hermetically sealed enclosures and constructions for use inendoscopic systems, particularly endoscopic systems with electronicimaging and illumination systems in the enclosures. Compound opticalwindows are also disclosed for use in the systems. The compound opticalwindows may have separate panes for an imaging system and anillumination system, and contrast-reducing optical boundaries arebetween panes.

Persons skilled in the art will recognize that many modifications andvariations are possible in the details, materials, and arrangements ofthe parts and actions which have been described and illustrated in orderto explain the nature of this inventive concept and that suchmodifications and variations do not depart from the spirit and scope ofthe teachings and claims contained therein.

All patent and non-patent literature cited herein is hereby incorporatedby references in its entirety for all purposes.

1. A handheld medical instrument having a lighting system forilluminating a target area, the system comprising: a light source forilluminating an intracorporeal target area, and an associated powercontroller, the system being configured to move from a firstillumination mode to a second illumination mode, corresponding to aselected power dissipated by the light source, in response to a scenechange sensed by the instrument; wherein the light source is disposedwithin a housing that comprises a handle of the instrument, the handleof the instrument is a user-graspable portion of the instrumentconfigured to be grasped by a user when the instrument is in active use,and the power controller maintains a temperature of the handle below apredetermined maximum temperature by controlling power to the lightsource based on an input from a temperature sensor mounted in thehandle.
 2. The medical instrument of claim 1 wherein the instrument isan endoscope.
 3. The medical instrument of claim 2 wherein the lightsource is disposed in a handle portion of the endoscope.
 4. The medicalinstrument of claim 2 wherein the light source is disposed in a distalinsertion end of the endoscope.
 5. The medical instrument of claim 2wherein an image sensor is disposed within a distal insertion portion ofthe endoscope.
 6. The medical instrument of claim 1 wherein an imagesensor is disposed within a distal insertion portion of the instrument.7. The medical instrument of claim 1 wherein the instrument isconfigured to sense a predetermined change of scene or brightness andmake a predetermined change in power to the light source based on thechange in scene, or lack thereof, or brightness.
 8. The medicalinstrument of claim 7, wherein the instrument comprises an endoscopewith a light source disposed within a housing of the endoscope.
 9. Themedical instrument of claim 8 wherein the instrument is configured tosense a predetermined change of temperature and make a predeterminedchange in power to the light source based on the change in temperature.10. The medical instrument of claim 7 wherein a set of predeterminedpixels in an image sensor is designated for providing signals that areprocessed to determine whether or not there is a predetermined change inscene or brightness.
 11. The medical instrument of claim 7 wherein thepredetermined maximum temperature is about 40 degrees C.
 12. The medicalinstrument of claim 1 wherein the instrument is battery powered.
 13. Themedical instrument of claim 1, further comprising an imaging systemcomprising a pixellated image sensor, wherein: the instrument isconfigured so that a state of activity of the instrument can bedetermined based, at least in part, on the sensed scene change, andwherein the sensed scene change corresponds to a signal from one or morepixels in the image sensor.
 14. The medical instrument of claim 13wherein a power dissipation for the instrument comprises a powerdissipation of the lighting system.
 15. The medical instrument of claim14 wherein the instrument is further configured so that a state ofinactivity of instrument use can be determined, at least in part, byprocessing signals from one or more pixels in the image sensor, andwherein the instrument is further configured such that the reduction inpower dissipated by the light source occurs after a predetermined periodof inactivity.
 16. The medical instrument of claim 1 wherein the inputcomprises a signal from a piezoelectric sensor or an accelerometerassociated with the instrument.